Here's what I did. Sign in to gmail using my regular gmail account. In settings "Add a mail account" and provide gmail pop3 and smtp settings with your email

Here's what I did. Sign in to gmail using my regular gmail account. In settings "Add a mail account" and provide gmail pop3 and smtp settings with your email address and credentials for your own domain. Now in gmail (signed in with regular gmail account) I have options for which account to send from (I can change the default for that).